Publish for a recent version of SBT

[nrinaudo]

Long story short, until very recently, SBT published plugins in a way that was non-standard enough that it made them impossible to retrieve from corporate tooling. The details are a little boring and don't make anybody look good, so let's leave it at that.

I was wondering if it'd be possible to update this project to use the current latest version of SBT and publish it again, in order to make it available to people in my situation - writing Scala, using Antlr, for work, at a big corporation.

Note that the plugin is simple enough that I can simply copy it as a local plugin to my build and that would work very quickly. This is not at all a blocker, just a nice improvement.